Materials used as refrigerants are typically chlorinated fluorocarbons, which are used because of their relative stability and non-flammability and because such materials boil and condense in a useful temperature and pressure range. An example of a chlorinated fluorocarbon refrigerant is the refrigerant sold under the trademark FREON by duPont de Nemours.
Until recently, such refrigerants were believed to be relatively inert and free of harmful side effects. Recently, however, it has been discovered that such refrigerants have a detrimental effect on the ozone layer above the earth when released into the atmosphere, such that it is now necessary to avoid open air release of refrigerants from equipment, such as refrigerators, air conditioning units, heat pumps and the like.
In normal use, refrigerants are constantly recycled within refrigeration equipment and are not released to the atmosphere. However, over time, refrigerants gradually become contaminated by water, air, compressor oil, hydrochloric acid, waxes, varnishes and the like, and lose their effectiveness. Such contaminants accelerate the rate of breakdown of the refrigerants and increase the operating temperatures of the compressors used in the refrigeration equipment. Prolonged operation of a refrigeration compressor at higher temperatures often causes compressor or compressor drive failure.
For many years, it was common practice in the industry simply to release the contaminated refrigerant to the atmosphere. Now, however, because of more stringent environmental regulations, such practice is no longer tolerated. It is therefore desirable in servicing refrigeration units to be able to recover the refrigerants in them and replace the refrigerants after servicing has been completed in a manner which substantially prevents any loss of either contaminated or pure refrigerants to the atmosphere.